Electromagnetic device



May 22, 1945. R. D. NELSON ELECTROMAGNETIC DEVICE I Filed Nov. 15, 1941 3 Sheets-Sheet 1 INVENTOR. AOllfl/VD 12 #5130 y 1945- R. D. NELSON ELECTROMAGNETIC DEVICE Filed Nov. '13, 1941 3 Sheets-Sheet 3 IN VEN TOR. POZZA/VD D. /V[LJ'0/V WW m 9 7 w 5 M f j. M W q q 7 Z .W 1 Z M/ W W .jl1 d w [4 MW f ATTOR EY.

Patented May 22, 1945 ELECTROMAGNETIC DEVICE Rolland D. Nelson, South Milwaukee, Wis., assignor to Line Material Company, South Mllwaukee, Wis., a corporation of Delaware Application November 13, 1941, Serial No. 418,876

16 Claims.

This invention relates to electromagnetic devices such as transformers, chokes, and other devices or this general nature,

Transformers have heretofore been made in which wound magnetic cores are employed. However, transformers having wound magnetic cores frequently require a considerable amount of assembly work and often require very great care in order to avoid the danger of imparting mechanical stresses to the magnetic core after the magnetic core has been annealed, as these mechanical stresses adversely affect the magnetic characteristics of the cores thereby resulting in a lowering of the efficiency of the transformer or other electromagnetic device.

This invention is designed to overcome the above noted defects and objects of this invention are to provide a novel form of electromagnetic device which, in its preferred form, has its core structure formed of wound magnetic ribbon, the major portion of the core structure being formed of closed wound cores and the remainingportion of its core structure being formed by winding a closed magnetic core from magnetic ribbon and thereafter cutting the wound closed structure into two sections both of which are used in the completed device, in which no unusual care is required in the assembly of the parts of the tievice, in which no bending, machining, or other working of the core structure is required after annealing, and in which short-circuiting f the laminations is avoided.

winding, or, as stated, a combination of both stacked magnetic laminations and Wound magnetic ribbon, in all forms the resulting magnetic core structure being laminated through its entire extent. 7

Further objects are to provide an electromagnetic device in which there are relatively few joints in the core structure, in which the joints in the core structure are so formed that a substantially edge to edge contact of the adjacent laminations is obtained, thereby materially reducing the reluctance of the magnetic path, and in which these results are obtained in a very simple manner and with a very small amount of work required in the manufacture of the device.

Further objects are to provide a novel construction of electromagnetic device in which the losses are relatively small, and in which a very good space factor is obtained tor the conducting winding.

Further objects are to provide a novel form of transformer or other electromagnetic device which is extremely simple to manufacture, and in which the number of operations required in its production is materially reduced.

Embodiments of the invention are shown in the accompanying drawings, in which:

' Figure 1 is a view, partly in section and partly broken away, showing a transformer.

Figure 2 is a top view of the structure shown in Figure 1, with parts broken away and parts in section.

Figure 3 is a side elevation .of the structure shown in Figure 1, such view being drawn to a smaller scale.

Figure 4 is a view of a further form of transformer.

Figure 5 is a of Figure 4.

Figure 6 is a sectional view on the line 6-6 of Figure 4.

Figure '7 is a view, partly insection and partly broken away, showing a further form of transformer.

Figure 8 is a sectional view on the line 8-8 of Figure 7.

Referring to the drawings, particularly Figures 1, 2 and 3, it will be seen that the transformer is formed of three mean portions, namely, two outer closed wound cores 1 formed of magnetic ribbon which may be of approximately rectangular shape as shown with the last convolution tacked down as indicated at 2 by brazing, weldihg or other similar means, and a central core section indicated generally at 3. The central core section is also a wound core formed of magnetic ribbon which is wound into an approxi-- mately rectangular shape and which is thereafter cut in half and the two half sections reversed and put together back to back to form the main :body of the central core as indicated at 3 in Figure 1, with the end portions of the central core projecting laterally at each end of the central core, such projecting portions being indicated by'the reference character 43. The end portions of the central core are positioned between the outer closed cores 0 in the finished transformer.

In making the transformer, the cores are all wound from magnetic ribbon on suitable mandrels to give the shape desired. Thereafter the central core is cut in half as previously described and the sides of the center core 3 are ground down, up to the lines indicated at 5 in Figure 1, and the sides of end portions t are ground down sectional view on the line 5-5 slightly to provide smooth flat faces. The grinding extends inwardly to a greater distance along the body of the central core} than along the portions 4 to thereby provide an air gap between the curved parts 6 of the central core'and the adjacent portions of the closed outer cores I, thus avoiding any short-circuiting across the laminations of the outer cores I, which would have been caused had the curved sections 5 of the central core contacted these laminations and formed a metal to metal contact. Instead, as stated, these curved sections 6 are ground down a 'sufilcient distance to keep them out of contact with the adjacent P rtions of the closed cores I. grinding need not extend throughout the entire length of the central core 3, though this is a simple way of doing it, for obviously the grinding may extend only along the area immediately adjacent and including the curved portions 6 at the ends of the central core 3 so as to provide the air gap hereinabove mentioned.

A further manner in which the central core may be treated would be to either grind the central core on both sides of the central core including the outwardly extending portions 4, or else grind merely that portion of the central core included between the outer wound cores I without grinding the central portion of the central core to a greater extent than the outer portions. When either of these two methods is followed, insulating paint would be placed on the central portion of the central core, particularly at its end portions 6 between the lines 5, 5 to thereby prevent short-circuiting of the laminations of the outer cores I. i

The grinding of the portions 4 is for the purpose of securing smooth, uniform side faces for these portions. It is preferable also to slightly grind the adjacent faces of the closed. cores I so that there will be a very intimate, close and ac curate contact between the portions 4 at the ends of the central core 3 and the adjacent portions of the closed cores I. Inasmuch as the laminations in the portions 4 are in parallelism with the adjacent lamlnations of the closed cores I, it is apparent that an edge to edge contact is secured between the laminations of the central core 3 and the laminations of the closed outer cores I and thus the reluctance at this joint is greatly reduced. Also it is to be noted from an examination of Figure 1 that an extended or long contact is secured at these portions of the structure, thus also materially reducing the reluctance of the joints at these points.

After the closed cores I have been wound with their ends secured as indicated at 2, and after the central core 3 has been wound and cut inhalf while it is held in a suitable clamping means .not shown, and after the grinding has been done on the central and closed cores as described hereinabove, these cores are held clamped by any suitable means so as to retain their shape and are then annealed. During the annealing any wire edges or burrs that may be left from the grinding or cutting are burned off, but if by chance any remaining burrs or wire edges should be left after annealing, these may be readily removed by means of a wire brush, or, in fact, they may be removed by a wire brush prior to annealing.

After the parts forming the core of the transformer have been annealed, they are not thereafter subject to any kind of machining, bending or other working and consequently they have no stresses imparted thereto, with the result, therefore, that their magnetic characteristics are unimpaired.

After the parts have been annealed, the central core 3 is placed in an ordinary winding lathe and the conducting winding 1 is wound thereon, suitable insulation being provided in the customary manner. After the central core 3 has been wound, it is then positioned between the closed outer cores I, and the parts are then clamped together to form the finished transformer. This clamping may be accomplished in any suitable manner. A very simple means is shown in Figures 1, 2 and 3 in which L-shaped angle irons 8 are provided and are drawn towards each other by means of bolts 9, all of the clamping structure, it being noted, being located wholly outside of the core structure of the transformer.

It is preferable to provide insulating sheets 10 between all of the faces of the clamping members and the core sections. It is to be noted also from Figures 2 and 3 that the L-shaped clamping members 8 extend over the ends 4 of the central core 3.

While it is preferable to slightly grind the portions 49.1; the ends of the center core 3 and the adjacent portions of the outer cores I, this grinding may be dispensed with if desired but as stated, more accurate and smoother faces are provided by grinding at these contacting portions.

Also if it is desired, any oxide or scale that may be formed on the portions 4 and on the adjacent portions of the outer core I may be removed after annealing, though this is not usually found necessary. This oxide may be scraped off or brushed off but it is to be distinctly understood that no machining or working of the cores takes place after annealing and thus no stresses are imparted to the cores after annealing. Instead, the transformer is finished after annealing without any stresses being imparted to any core structure whatsoever and thus minimum reluctance of the core sections'is obtained in the finished transformer.

In the form of the invention shown in Figures 4, 5 and 6 outer closed cores H are wound from magnetic ribbon and the central core I2 is also wound from magnetic ribbon. The central core is either cut in half or a portion is cut out so as to provide a central core of the shape shown in Figure 5 wherein the outer ends of the central core are cut off along the lines indicated at 13 in Figure 5.

The central core is, of course, held clamped during this cutting operation as in the case of the form previously described and the faces at the points l3 and the adjacent portions of the closed cores are ground to provide smooth surfaces. The central core I! and the outer closed cores II are held clamped so as to retain their shape and are annealed. Thereafter the central core is either slipped through a preformed conducting winding M, as the curved end portions l5 thereof do not extend beyond the outline of the central core, or, if desired, the central core maybe placed in a winding lathe and the conducting winding l4 may be wound thereon, suitable insulation being provided in accordance with the usual practice.

All of the cutting and grinding is done prior to annealing and after annealing no further working either by machining, bending or in any other manner is done on any of the core structures, thereby avoiding stressing the core structures after annealing. During the annealing any wire edges or burrs that may be left from the grinding or cutting are burned off, but if by chance any remaining burrs or wire edges should be left after annealing, these may be readily removed by means of a wire brush, or, in fact, they may be removed by a wire brush prior to annealing.

The final step in the manufacture of this form of the invention is to clamp the outer cores to the central core. This is readily accomplished in a simple way, for example by means of the cores ll, V-shaped clamping members are provided at opposite ends of the transformer. These V-shaped clamping plates are forced inwardly by means of set screws 2| threaded into the brackets IS, the brackets themselves being held against opening outwardly by means of the bolts 22. It is also preferable to provide insulating sheets 23 between the ends l5 of the central core and the clamping member 20.

While it is not usually necessary; if it is desired portions 21, see Figure 8, which do not cross over the curved outer ends of the central core, see Figure 7.

The wound magnetic ribbons forming the outer and central cores are held clamped during the cutting, grinding and annealing portions as previously described. Obviously any oxide that may be formed on the ground faces may be scraped off if desired prior to assembly as previously described. It is to be distinctly understood, however, that no machining, bending or working of any of the coresections occurs after annealing.

While it is preferred to wind all of the core sections and out certain of them in different forms of the invention, it is within the province of this invention to form all of the core sections, except the outer closed core sections of the first two forms of the invention, of stacked magnetic laminations which are shaped as required, though this is not the preferred form of the invention.

The central core 24 may be placed in an ordinary winding lathe and the conducting winding is wound thereon, suitable insulation being pro- 1 vided in the customary manner.

any oxide that may be formed along the faces manner, but no working of any of the core structures whatsoever is done after the annealing has been completed and thus the core sections are left in a wholly unstressed condition in the finished transformer.

In the form of the invention shown in Figures 7 and 8 the central core is formed by winding 9. closed core of magnetic ribbon as described in connection with the central core of Figures 1, -2 and 3. This wound magnetic ribbon is then cut in half and the two sections are arranged back to back to form the central core portion 24 provided with outwardly extending end portions 25 projecting outwardly in opposite directions at each end of the central core.

The outer cores are formed of wound magnetic ribbon and are cut in half and the two halves are separated. The half sections forming the outer cores are indicated at 26 and each is provided with inwardly projecting end portions 21 which are spaced apart, as shown most clearly in Figure 8. These end portions 21 abut the side faces of the end portions 25 of the central core section and an edge to edge contact is obtained. It is preferable to grind the adjacent faces of the portions 25 and 21 to secure smooth even faces and an accurate edge to edge contact. After the grinding has been completed, all of the cores are annealed and any burrs or wire edges that may result from the grinding or cutting are burned off, but if by any chance any remaining burr or wire edges should be left after annealing, these may be readily removed by means of a, wire brush or, in fact, they may be removed by a wire brush prior to annealing.

It is not necessary to grind down the central portion of the central core 24 for it will be seen that in this form of the invention the outer cores do not cross over the curved portions at the outer ends of the central core, as in the case of Figure 1. Instead the outer cores terminate in the The several sections of the core may be clamped together in any desired way. For example, the L-shaped clamping members 8 may be employed which are drawn towards each other by means of the bolts 9, suitable insulation in being provided between the clamping members and the laminated core structure as described in connection with the form of the invention shown in Figures 1 to 3.

The material used in the making of the cores is any suitable magnetic ribbon. It is preferable to use silicon steel which may be either hot rolled .or cold rolled as this material has been found highly efficient in the manufacture of these transformers or other electromagnetic devices of this general nature, such as chokes for instance.

In the forms of the invention shown in Figures 1, 2, 3, 7 and 8 the lateral edges of the laminations of the central core have an edge to edge contact with the adjacent edges of the outer cores. In the form of the invention shown in Figures 4, 5 and 6 the end edges of the laminations of the central core i2 have an edge to edge contact with the adjacent laminations of the outer closed cores ii. In all forms of the invention, therefore, this edge to edge contact is secured between the laminations of the central core and the laminations of the outer cores.

It is to be noted that in all forms of the invention the magnetic flux travels lengthwise of the magnetic ribbon in substantially all portions of the core structure and this is the path having minimum magnetic reluctance due to the manner in which the particles of the magnetic ribbon are orientated during their manufacture. However, there is, a small portion of the path of the magnetic flux where the flux travels crosswise of the magnetic ribbon where it passes, for example in Figures 1, 2, 3, 7 and 8, from the end portions of the central core into the outer cores. This path of cross travel of the fiux is very short and is confined to a very limited portion of the entire core structure. shown in Figures 4, 5 and 6 there is no cross travel of the flux in the end portions iii of the In the form of the invention and other electromagnetic devices have been disclosed by this invention which have a Very small magnetic reluctance for the flux travel and which are extremely simple to make and which, in their preferred forms, utilize the advantages oi wound magnetic cores formed from magnetic ribbon, though allowing the conducting winding to be wound in the ordinary simple manner without requiring-any special processes for the winding of the conducting winding.

It is to be noted that the substantially edge to edge contact between the laminations of the central and outer cores materially reduces the reluctance of the magnetic path.

It will be seen further that transformers or other electromagnetic devices constructed in accordance with this invention may be made with a very small number of operations and in a very simple manner.

Wherever the expression insulating paint is used, it is intended to cover insulating paint,

insulating varnish, or any other insulating com-- pound. It is also to be understood that wherever the expressions "laminations or "magnetic laminations are employed, it is intended that these expressions shall not be limited to stacked laminations but shall include any laminated structure whether it is formed by winding a magnetic ribbon or by stacking magnetic laminations.

Although this invention has been described in considerable detal, it is to be understood that such description is intended as illustrative rather than limiting, as the invention may be variously embodied and is to be interpreted as claimed.

I claim:

l. A core construction for an electromagnetic device comprising a pair of outer, closed, laminated, wound cores formed of magnetic ribbon, and

a central core formed of magnetic laminations,

Said central core having its ends located between the closed cores, the laminations of the central and closed cores being arranged with their edges in close juxtaposition and lying in parallel planes and with the longitudinal extent of the edges of the individual laminations of the central core substantially paralleling the longitudinal extent of the edges of the individual laminations of the outer cores at their area of juxtaposition.

2.. A core construction for an electromagnetc device comprising-a pair of outer, closed, laminated, wound cores formed or magnetic ribbon, and a central core formed of magnetic laminations, sa d central core having its ends located between the closed cores, the laminations of the central core having an edge to edge contact with the laminations of the closed cores w'th the contactin edges of the central and closed cores lying in parallel planes and with the longitudinal extent of the edges of the individual laminations oi the ends of the central core substantially paralleling the longitudinal extent of the edges of the adjacent laminations of the outer cores.

3. A core construction for an electromagnetic device comprising a pair of outer, closer, lamiinated, wound cores formed of magnetic ribbon, a central core formed of magnetic laminations, said central core having its ends located b:tween the closed cores, the laminations of .the central core having an edge to edge contact with the laminations of the closed cores with the contacting edges of the central and closed cores arranged in substantial parallelism, and clamping means for spreading the ends of the central core and for maintaining an edge to edge contact between the laminations oi the central and closed cores.

4. A core construction for an electromagnetic device comprising a pair of outer, closed, laminated, wound cores formed of magnetic" ribbon, and a central core formed of magnetic laminations, the laminations at each end of the central core extending in opposite directions, said central core having its ends located between the closed cores, the edges of the laminations of the end portions of the central core and the adjacent edges of the outer cores being closely juxtaposed and lying in parallel planes with the longitudinal extent of the edges of the individual laminations 01' the ends of the central core substantially paralleling the adjacent longitudinal extent of the edges of the individual laminations of the outer cores, said central and closed cores being annealed and being free from any stresses produced by machining or other working after annealing.

5. A core construction for an electromagnetic device comprising a pair of outer. closed, laminated, wound cores formed of magnetic ribbon, and a central core formed of magnetic laminations.

the laminations at each end of the central core being turned in opposite directions, the ends of the central core being positioned between the closed cores and the end portions of the laminations of the central core extending at substantially right angles to the adjacent laminations of the closed cores and having a substantial edge to edge contact with the adjacent laminations of the outer closed cores.

6. A core construction for an electromagnetic device comprising a pair of outer. closed, laminated, wound cores formed of magnetic ribbon, and a central magnetic core formed of magnetic laminations with the laminations extending in opposite directions at each end to form end portions, the end portions of the central core being located between the closed cores, the laminations of the end portions of the central core havin substant ally an edge to edge contact with the adjacent laminations of the closed cores, the edges of the laminations or the end portions of the central core and the adjacent edges of the laminations of the outer cores lying in parallel p anes and the longitudinal extent of the edges of the individual laminations of the end portions of the central core substantially paralleling the longitudinal extent of the adjacent edges of the individual laminations of the outer cores.

'1. A core construction-for an electromagnetic device comprising a pa r of outer, closed, laminated, wound cores formed of magnetic ribbon. and a central core formed of magnetic laminations having projecting endportions parts of which are curved and the outer ends of which extend in opposite directions, the outer ends of the laminations of the central core being wider than the curved portions, the ends of the central core being located between the closed cores with the side edges of the outwardly extending portions of the ends of the laminations of the central core having an edge to edge contact with the laminations of the closed cores and with the curved portions of the ends of the central core out of contact with the laminations of the closed cores.

8. A core construction for an electromagnetic device comprising a pair of outer. closed, laminated, wound cores formed of magnetic ribbon, and a central magnetic core formed of magnetic laminations with the laminations extending outwardly in opposite directions at each end to form end portions, the oppositely extending portions having a greater width than the remaining portions 'of the central core and being located between the closed cores, the side edges of the laminations of the oppositely extending portions at the ends of the central cor having substantially an edge to edge contact with the adjacent edges of the laminations of the closed cores.

9. A core construction for an electromagnetic device comprising a pair of outer, closed, laminated, wound cores formed of magnetic ribbon, and a central magnetic core formed of magnetic laminations with the laminations turned outwardly in opposite directions at each end to form end portions, the oppositely turned end portions 01' the central core being located between the closed cores with the ends of the laminations of the central core having substantially an edge to edge contact with the adjacent edges of the laminations of the closed cores.

10. A core construction for an electromagnetic device comprising a pair of outer, closed, laminated, wound cores formed of magnetic ribbon, and a central core formed of magnetic laminations with the laminations extending outwardly in opposite directions at each end to form end portions projecting outwardly laterally beyond sides between the oppositely extending end portions.

11. A core construction for an electromagnetic device comprising a pair of outer, closed, laminated, wound cores formed of magnetic ribbon, and a central magnetic core formed of magnetic laminations with the laminations extending in opposite directions at each end to form end portions, said central magnetic core being formed of two portions of a closed wound core of magnetic tral core substantially paralleling the longitudinal extent of the edges of the individual laminations of the outer core at their area of juxtaposition.

13. A core construction for an electromagnetic device comprising'a pair of outer, closed, laminated, wound cores formed of magnetic ribbon, at central core formed of magnetic laminations, the laminations at each end of the central core being turned in opposite directions, the ends of the central core being positioned between the closed cores and the end portions of the laminations of the central core extending at substantially right angles to the adjacent laminations of the closed cores, and clamping means including 4 turned in opposite directions, the ends of the central core being positioned between the closed cores and the end portions of the laminations of the central core extending at substantially right angles to the adjacent laminations of the closed cores, and clamping means for holding the portions of. the core togethensaid clamping means including 'main frame like means and tapered wedging means located at each end of the central core movable withreference to the main frame like means and bearing against the outwardly turned end portions of the central core.

15. A core construction for an electromagnetic device comprising a central core having a pair of sections formed of magnetic laminations with the end portions turned outwardly in opposite direc-. tions at each end of the central core and with the outer ends of the end portions spaced apart at each end of the central core, and an outer core structure formed of magnetic laminations with ribbon cut across with the two resulting portions arranged back to back to form the central core,

the end portions of the central core being located between the closed cores, the laminations or the end portions of the central core and the laminations of the adjacent portions or the outer cores having their edges in close juxtaposition and lying in parallel planes with the longitudinal extent or the edges of the individual laminations of the central core substantially paralleling the longitudinal extent 0! the edges or individual laminations or the outer cores at their area of juxtaposition.

12. A core construction for an electromagnetic device comprising at least one outer closed, laminated, wound core formed of magnetic ribbon, and a central magnetic core formed of magnetic laminations with the laminations extending in opposite directions at each end to form end portions, the end portions 01' the central core bein located in close juxtaposition to portions of the g outer closed core and to one side thereof with the laminations oi the end portions of the central core and the laminations of the adjacent portions of the outer core having their edges lying in parallel planes with the longitudinal extent of the edges or the individual laminations of the centhe side edges of the laminations of the outer core structure in close juxtaposition to the side edges of the outwardly turned ends of the central core, the edges of the outwardly turned end portions of the central core and the edges of the outer core structure lying in parallel planes with the longitudinal extent of the edges of the individual laminations of the outwardly turned end portions of the central core substantially paralleling the longitudinal extent of the adjacent edges of the individual laminations of the outer core structure.

16. A core construction for an electromagnetic device comprising a central core having a pair of sections formed of magnetic laminations with the end portions turned outwardly in opposite directions at each end of the central core and with the outer ends of the end portions spaced apart at each end of the central core, and an outer core structure formed or magnetic laminations with the. side edges" of the laminations of the outer core structure in contact with the side edges of the outwardly turned ends of the central core,

the edges of the outwardly turned end portions tithe central core and the edges of the outer core structure lying in parallel planes with the longitudinal extent of the'edges of the individual laminations of the outwardly turned end portions 01- v the central core substantially paralleling the ion- 

